EAGER: Application of Cluster Expansion Method to First-Principles Mineralogy

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Since 2004, it has become clear that there is a transition between two different crystal structures affecting the major mineral present deep in the Earth?s mantle, or, within about 200 km of the boundary with the Earth's core. Experimental studies of this perovskite to post-perovskite transition are challenging, fragmentary and, when iron is included, mutually contradictory. This EaGER award will enable a preliminary computational study to complement some ongoing experimental efforts. Methods necessary to understand minerals with many possible atomic arrangements, widespread in modern materials science but little known in mineral physics, will be employed.The importance of proper treatment of atomic arrangements in solid solutions, both for obtaining the configurational entropy and in its effect on the vibrational terms, seems to be little understood in the mineralogical community; many studies in computational mineral physics will benefit from raising the level of awareness of solid solutions and the availability of tools to address them. This work is intended to demonstrate their suitability for detailed follow-up studies of lower mantle mineralogy and also to spark a revolution in extension of first-principles methods beyond one-component systems, while training a graduate student with broad abilities in computational thermodynamics, experimental mineral physics, observational astronomy, and theoretical geophysical fluid dynamics.